Copper removal of liquid steel containing 0.25 % carbon using Fe₂O₃-CaCl₂-SiO₂ flux

Abstract

Copper is recognized as one of the most detrimental residual elements in steelmaking due to its adverse effects during the thermo-mechanical processing of steel. Selective chlorination volatilization has emerged as a promising method for removing residual copper from liquid steel. In this study, the selective chlorination behavior of copper was systematically investigated using Fe₂O₃-CaCl₂-SiO₂ flux at 1873 K, focusing on optimizing flux composition parameters: Fe₂O₃/Cu molar ratio (n(Fe₂O₃)/n(Cu)), CaCl₂/Cu molar ratio (n(CaCl₂)/n(Cu)), and SiO₂/CaCl₂ molar ratio (n(SiO₂)/n(CaCl₂)). Experimental results demonstrated an ideal copper removal ratio of 39.68 % under optimized conditions, achieved with a flux composition of n(Fe₂O₃)/n(Cu) = 10.0, n(CaCl₂)/n(Cu) = 1.0, and n(SiO₂)/n(CaCl₂) = 1.0. Phase analysis revealed that the primary chlorination volatiles consisted of CuOHCl, Cu₂Cl(OH)₃, and FeCl₂(H₂O)₂, confirming the mechanistic pathway of copper removal. This work substantiates the technical feasibility of selective chlorination for copper elimination from liquid steel and provides a viable strategy for enhancing scrap steel recycling in sustainable metallurgical practices. The proposed method demonstrates significant potential for industrial application in residual element control.